Method for allocating uplink resources in a wireless communication system and a device therefor

ABSTRACT

The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for allocating uplink resources in the wireless communication system, the method comprising: transmitting, by a first eNB to a second eNB, uplink (UL) resource allocation information for a user equipment (UE) connected with both the first eNB and the second eNB; receiving, by a first eNB from the UE, buffer size information; allocating one or more UL resources to the UE, by considering both of the buffer size information and the UL resource allocation information, wherein the UL resource allocation information indicates a ratio of the buffer size to be considered in each eNB.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/786,293, filed on Oct. 22, 2015, now U.S. Pat. No. 10,251,171, whichis the National Stage filing under 35 U.S.C. 371 of InternationalApplication No. PCT/KR2014/003939, filed on May 2, 2014, which claimsthe benefit of U.S. Provisional Application No. 61/823,404, filed on May15, 2013, the contents of which are all hereby incorporated by referenceherein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method for allocating uplink resources and adevice therefor.

BACKGROUND ART

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARQ)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTEbased on wideband code division multiple access (WCDMA), the demands andexpectations of users and service providers are on the rise. Inaddition, considering other radio access technologies under development,new technological evolution is required to secure high competitivenessin the future. Decrease in cost per bit, increase in serviceavailability, flexible use of frequency bands, a simplified structure,an open interface, appropriate power consumption of UEs, and the likeare required.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ina method and device for allocating uplink resource in a wirelesscommunication system. The technical problems solved by the presentinvention are not limited to the above technical problems and thoseskilled in the art may understand other technical problems from thefollowing description.

Technical Solution

The object of the present invention can be achieved by providing amethod for operating by an evolved-Node B in wireless communicationsystem, the method comprising; transmitting, by a first eNB to a secondeNB, uplink (UL) resource allocation information for a user equipment(UE) connected with both the first eNB and the second eNB; receiving, bythe first eNB, buffer size information from the UE; and allocating, bythe first eNB, one or more UL resources to the UE by considering both ofthe buffer size information and the UL resource allocation information,wherein the UL resource allocation information indicates a ratio of thebuffer size to be considered in each eNB.

In another aspect of the present invention, a method for an evolved-NodeB in wireless communication system, the method comprising; receiving, bya second eNB from a first eNB, uplink (UL) resource allocationinformation for a user equipment (UE) connected with both the first eNBand the second eNB; receiving, by the second eNB, buffer sizeinformation from the UE; and allocating, by the second eNB, one or moreUL resources to the UE by considering both of the buffer sizeinformation and the UL resource allocation information, wherein the ULresource allocation information indicates a ratio of the buffer size tobe considered in the second eNB.

In another aspect of the present invention, provided herein is anevolved-Node B in the wireless communication system, the eNB comprising:an RF (radio frequency) module; and a processor configured to controlthe RF module, wherein the processor is configured to transmit uplink(UL) resource allocation information to a second eNB for a userequipment (UE) connected with both the first eNB and the second eNB, toreceive buffer size information from the UE, to allocate one or more ULresources to the UE by considering both of the buffer size informationand the UL resource allocation information, wherein the UL resourceallocation information indicates a ratio of the buffer size to beconsidered in each eNB.

Preferably, said transmitting comprising transmitting the UL resourceallocation information through an X2 interface.

Preferably, the ratio of the buffer size is configured per radio bearercomprising one Packet Data Convergence Protocol (PDCP) entity, two RadioLink Control (RLC) entities and two Medium Access Control (MAC) entitiesfor one direction.

Preferably, the buffer size information comprises amount of dataavailable for transmission in a Packet Data Convergence Protocol (PDCP)entity and amount of data available for transmission in a Radio LinkControl (RLC) entity.

Preferably, a first type cell including the first eNB provides serviceto a first area larger than a second area served by a second cellincluding the second eNB.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

According to the present invention, allocating resources can beefficiently performed in a wireless communication system. Specifically,the eNB (evolved-Node B) can allocates UL resources by considering botha ratio of a buffer size to be considered in each eNB and buffer sizeinformation reported by the UE.

It will be appreciated by persons skilled in the art that that theeffects achieved by the present invention are not limited to what hasbeen particularly described hereinabove and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS), and FIG. 2B is ablock diagram depicting architecture of a typical E-UTRAN and a typicalEPC;

FIGS. 3A and 3B are diagrams showing a control plane and a user plane ofa radio interface protocol between a UE and an E-UTRAN based on a 3rdgeneration partnership project (3GPP) radio access network standard;

FIG. 4 is a diagram of an example physical channel structure used in anE-UMTS system;

FIG. 5 is a conceptual diagram for dual connectivity between a macrocell and a small cell;

FIG. 6A is a conceptual diagram for C-Plane connectivity of basestations involved in dual connectivity, and FIG. 6B is a conceptualdiagram for U-Plane connectivity of base stations involved in dualconnectivity;

FIGS. 7 and 8 are conceptual diagrams for radio protocol architecturefor dual connectivity;

FIGS. 9 and 10 are conceptual diagrams for allocating UL resourcesaccording to embodiments of the present invention;

FIG. 11 is conceptual diagram an exemplary allocation of UL resourcesaccording to embodiments of the present invention; and

FIG. 12 is a block diagram of a communication apparatus according to anembodiment of the present invention.

BEST MODE

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Hereinafter, structures, operations, and other features of the presentinvention will be readily understood from the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using along term evolution (LTE) system and a LTE-advanced (LTE-A) system inthe present specification, they are purely exemplary. Therefore, theembodiments of the present invention are applicable to any othercommunication system corresponding to the above definition. In addition,although the embodiments of the present invention are described based ona frequency division duplex (FDD) scheme in the present specification,the embodiments of the present invention may be easily modified andapplied to a half-duplex FDD (H-FDD) scheme or a time division duplex(TDD) scheme.

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2A, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

FIG. 2B is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 2B, an eNodeB 20 provides end points of a userplane and a control plane to the UE 10. MME/SAE gateway 30 provides anend point of a session and mobility management function for UE 10. TheeNodeB and MME/SAE gateway may be connected via an S1 interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signaling to eNodeBs20, NAS signaling security, AS Security control, Inter CN node signalingfor mobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the S1 interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIGS. 3A and 3B are diagrams showing a control plane and a user plane ofa radio interface protocol between a UE and an E-UTRAN based on a 3GPPradio access network standard. The control plane refers to a path usedfor transmitting control messages used for managing a call between theUE and the E-UTRAN. The user plane refers to a path used fortransmitting data generated in an application layer, e.g., voice data orInternet packet data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a medium access control (MAC) layer located on the higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel Data is transported betweena physical layer of a transmitting side and a physical layer of areceiving side via physical channels. The physical channels use time andfrequency as radio resources. In detail, the physical channel ismodulated using an orthogonal frequency division multiple access (OFDMA)scheme in downlink and is modulated using a single carrier frequencydivision multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer of a higher layer via a logical channel. The RLClayer of the second layer supports reliable data transmission. Afunction of the RLC layer may be implemented by a functional block ofthe MAC layer. A packet data convergence protocol (PDCP) layer of thesecond layer performs a header compression function to reduceunnecessary control information for efficient transmission of anInternet protocol (IP) packet such as an IP version 4 (IPv4) packet oran IP version 6 (IPv6) packet in a radio interface having a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. In FIG. 4, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information. A transmission time interval(TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receive the PDSCH indicated by B and C in the PDCCHinformation.

FIG. 5 is a conceptual diagram for dual connectivity between a macrocell and a small cell.

In the next system of LTE-A, a plurality of small cells (e.g, microcell, pico cell etc.) may be present in a big cell (e.g. macro cell)having larger coverage than the small cells for optimization of datatraffic, etc. For example, a macro cell and a micro cell may be combinedfor one user equipment (e.g. the dual connectivity). If the macro cellis used for managing mobility of the UE mainly (e.g. PCell) and themicro cell is used for boosting throughput mainly in this situation(e.g. SCell), the plurality of cells combined to the UE have differentcoverage each other. And each of cells can be managed by each of basestations. The base stations may be geographically separated (inter-siteCA).

The dual connectivity means that the UE can be connected to both themacro cell and the small cell at the same time. With dual connectivity,some of the data radio bearers (DRBs) can be offloaded to the small cellto provide high throughput while keeping scheduling radio bearers (SRBs)or other DRBs in the macro cell to reduce the handover possibility. Themacro cell is operated by MeNB (Macro cell eNB) via the frequency of f1,and the small cell is operated by SeNB (Small cell eNB) via thefrequency of f2. The frequency f1 and f2 may be equal. The backhaulinterface (BH) between MeNB and SeNB is non-ideal, which means thatthere is considerable delay in the backhaul and therefore thecentralized scheduling in one node is not possible.

To benefit from the dual connectivity, the best-effort traffic which isdelay tolerant is offloaded to small cell while the other traffic, e.gSRBs or real-time traffic, is still serviced by the macro cell.

FIG. 6A shows C-plane (Control Plane) connectivity of eNBs involved indual connectivity for a certain UE: The MeNB is C-plane connected to theMME via S1-MME (S1 for the control plane), the MeNB and the SeNB areinterconnected via X2-C(X2-Control plane). As FIG. 6A, Inter-eNB controlplane signaling for dual connectivity is performed by means of X2interface signaling. Control plane signaling towards the MME isperformed by means of S1 interface signaling. There is only one S1-MMEconnection per UE between the MeNB and the MME. Each eNB should be ableto handle UEs independently, i.e. provide the PCell (Primary Cell) tosome UEs while providing SCell(s) (Secondary Cells) for SCG to others.Each eNB involved in dual connectivity for a certain UE owns its radioresources and is primarily responsible for allocating radio resources ofits cells, respective coordination between MeNB and SeNB is performed bymeans of X2 interface signaling.

FIG. 6B shows U-plane connectivity of eNBs involved in dual connectivityfor a certain UE. U-plane connectivity depends on the bearer optionconfigured: i) For MCG bearers, the MeNB is U-plane connected to theS-GW via S1-U, the SeNB is not involved in the transport of user planedata, ii) For split bearers, the MeNB is U-plane connected to the S-GWvia S1-U and in addition, the MeNB and the SeNB are interconnected viaX2-U, and iii) For SCG bearers, the SeNB is directly connected with theS-GW via S1-U. If only MCG and split bearers are configured, there is noS1-U termination in the SeNB. In the dual connectivity, enhancement ofthe small cell is required in order to data offloading from the group ofmacro cells to the group of small cells. Since the small cells can bedeployed apart from the macro cells, multiple schedulers can beseparately located in different nodes and operate independently from theUE point of view. This means that different scheduling node wouldencounter different radio resource environment, and hence, eachscheduling node may have different scheduling results.

FIG. 7 is a conceptual diagram for radio protocol architecture for dualconnectivity.

E-UTRAN of the present example can support dual connectivity (DC)operation whereby a multiple receptions/transmissions (RX/TX) UE inRRC_CONNECTED is configured to utilize radio resources provided by twodistinct schedulers, located in two eNBs (or base stations) connectedvia a non-ideal backhaul over the X2 interface. The eNBs involved indual connectivity for a certain UE may assume two different roles: aneNB may either act as the MeNB or as the SeNB. In dual connectivity, aUE can be connected to one MeNB and one SeNB.

In the dual connectivity (DC) operation, the radio protocol architecturethat a particular bearer uses depends on how the bearer is setup. Threealternatives exist, MCG (Master Cell Group) bearer (RB-a), split bearer(RB-b) and SCG (Secondary Cell Group) bearer (RB-c). Those threealternatives are depicted on FIG. 7. The SRBs (Signaling Radio Bearers)are always of the MCG bearer and therefore only use the radio resourcesprovided by the MeNB. The MCG (Master Cell Group) bearer (RB-a) is aradio protocol only located in the MeNB to use MeNB resources only inthe dual connectivity. And the SCG (Secondary Cell Group) bearer (RB-c)is a radio protocol only located in the SeNB to use SeNB resources inthe dual connectivity.

Specially, the split bearer (RB-b) is a radio protocol located in boththe MeNB and the SeNB to use both MeNB and SeNB resources in the dualconnectivity and the split bearer (RB-b) may be a radio bearercomprising one Packet Data Convergence Protocol (PDCP) entity, two RadioLink Control (RLC) entities and two Medium Access Control (MAC) entitiesfor one direction.

Specially, the dual connectivity (DC) operation can also be described ashaving at least one bearer configured to use radio resources provided bythe SeNB.

FIG. 8 is a conceptual diagram for radio protocol architecture for dualconnectivity.

‘Data available for transmission’ is defined in PDCP and RLC layers tobe used for Buffer Status Reporting (BSR), Logical ChannelPrioritization (LCP), and Random Access Preamble Group (RAPG) selectionin MAC layer.

For the purpose of MAC buffer status reporting, the UE may consider thefollowing as data available for transmission in the RLC layer:

-   -   RLC SDUs (Service Data Unit), or segments thereof, that have not        yet been included in an RLC data PDU (Protocol Data Unit);    -   RLC data PDUs, or portions thereof, that are pending for        retransmission (RLC AM).

In addition, if a STATUS PDU has been triggered and t-StatusProhibit isnot running or has expired, the UE may estimate the size of the STATUSPDU that will be transmitted in the next transmission opportunity, andconsider this as data available for transmission in the RLC layer.

Meanwhile, for the purpose of MAC buffer status reporting, the UE mayconsider PDCP Control PDUs, as well as the following as data availablefor transmission in the PDCP layer:

For SDUs for which no PDU has been submitted to lower layers:

-   -   the SDU itself, if the SDU has not yet been processed by PDCP,        or    -   the PDU if the SDU has been processed by PDCP.

In addition, for radio bearers that are mapped on RLC AM, if the PDCPentity has previously performed the re-establishment procedure, the UEmay also consider the following as data available for transmission inthe PDCP layer:

For SDUs for which a corresponding PDU has only been submitted to lowerlayers prior to the PDCP re-establishment, starting from the first SDUfor which the delivery of the corresponding PDUs has not been confirmedby the lower layer, except the SDUs which are indicated as successfullydelivered by the PDCP status report, if received:

-   -   the SDU, if it has not yet been processed by PDCP, or    -   the PDU once it has been processed by PDCP.

In the prior art, there are only one PDCP entity and one RLC entity forone direction (i.e. uplink or downlink) in a Radio Bearer, and thus,when the UE calculates ‘data available for transmission’, it just sumsup the data available for transmission in PDCP and that in RLC. In LTERel-12, however, a new study on Small Cell Enhancement is started, wherethe dual connectivity is supported.

To support dual connectivity, one of the potential solutions is for theUE to transmit data to both Macro cell and Small cell utilizing a new RBstructure called dual RLC/MAC scheme, where a single RB has one PDCPentity, two RLC entities and two MAC entities for one direction, andRLC/MAC pair is configured for each cell, as shown in FIG. 8. In theFIG. 8, RB-B is called as “split Radio Bearer” and stands for DRB forBest Effort traffic.

Buffer Status Reporting (BSR)

The Buffer Status Reporting (BSR) procedure is used to provide a servingeNB with information about the amount of data available for transmission(DAT) in the UL buffers of the UE. RRC may control BSR reporting byconfiguring the two timers periodicBSR-Timer and retxBSR-Timer and by,for each logical channel, optionally signalling logicalChannelGroupwhich allocates the logical channel to an LCG (Logical Channel Group).

For the Buffer Status reporting procedure, the UE may consider all radiobearers which are not suspended and may consider radio bearers which aresuspended. A Buffer Status Report (BSR) may be triggered if any of thefollowing events occur:

-   -   UL data, for a logical channel which belongs to a LCG, becomes        available for transmission in the RLC entity or in the PDCP        entity and either the data belongs to a logical channel with        higher priority than the priorities of the logical channels        which belong to any LCG and for which data is already available        for transmission, or there is no data available for transmission        for any of the logical channels which belong to a LCG, in which        case the BSR is referred below to as “Regular BSR”;    -   UL resources are allocated and number of padding bits is equal        to or larger than the size of the Buffer Status Report MAC        control element plus its subheader, in which case the BSR is        referred below to as “Padding BSR”;    -   retxBSR-Timer expires and the UE has data available for        transmission for any of the logical channels which belong to a        LCG, in which case the BSR is referred below to as “Regular        BSR”;    -   periodicBSR-Timer expires, in which case the BSR is referred        below to as “Periodic BSR”.

A MAC PDU may contain at most one MAC BSR control element, even whenmultiple events trigger a BSR by the time a BSR can be transmitted inwhich case the Regular BSR and the Periodic BSR shall have precedenceover the padding BSR.

The UE may restart retxBSR-Timer upon indication of a grant fortransmission of new data on any UL-SCH.

All triggered BSRs may be cancelled in case UL grants in this subframecan accommodate all pending data available for transmission but is notsufficient to additionally accommodate the BSR MAC control element plusits subheader. All triggered BSRs shall be cancelled when a BSR isincluded in a MAC PDU for transmission.

The UE shall transmit at most one Regular/Periodic BSR in a TTI. If theUE is requested to transmit multiple MAC PDUs in a TTI, it may include apadding BSR in any of the MAC PDUs which do not contain aRegular/Periodic BSR.

All BSRs transmitted in a TTI always reflect the buffer status after allMAC PDUs have been built for this TTI. Each LCG shall report at the mostone buffer status value per TTI and this value shall be reported in allBSRs reporting buffer status for this LCG.

Logical Channel Prioritization (LCP)

The Logical Channel Prioritization procedure is applied when a newtransmission is performed. RRC may control the scheduling of uplink databy signaling for each logical channel: priority where an increasingpriority value indicates a lower priority level, prioritisedBitRatewhich sets the Prioritized Bit Rate (PBR), bucketSizeDuration which setsthe Bucket Size Duration (BSD).

The UE may maintain a variable Bj for each logical channel j. Bj may beinitialized to zero when the related logical channel is established, andincremented by the product PBR×TTI duration for each TTI, where PBR isPrioritized Bit Rate of logical channel j. However, the value of Bj cannever exceed the bucket size and if the value of Bj is larger than thebucket size of logical channel j, it may be set to the bucket size. Thebucket size of a logical channel is equal to PBR×BSD, where PBR and BSDare configured by upper layers.

Random Access Preamble Group (RAPG) Selection

The Random Access Resource selection procedure may be performed asfollows:

-   -   If ra-PreambleIndex (Random Access Preamble) and        ra-PRACH-MaskIndex (PRACH Mask Index) have been explicitly        signalled and ra-PreambleIndex is not 000000: the Random Access        Preamble and the PRACH Mask Index are those explicitly        signalled.    -   else the Random Access Preamble may be selected by the UE as        follows:

i) if Msg3 has not yet been transmitted, the UE may, and if RandomAccess Preambles group B exists and if the potential message size (dataavailable for transmission plus MAC header and, where required, MACcontrol elements) is greater than messageSizeGroupA and if the pathlossis less than PCMAX,c (of the Serving Cell performing the Random AccessProcedure)−preamblelnitialReceivedTargetPower−deltaPreambleMsg3−messagePowerOffsetGroupB,then UE may select the Random Access Preambles group B;

ii) else: the UE may select the Random Access Preambles group A.

In this case, the MAC functions addressed above, i.e. BSR, LCP, and RAPGselection, are performed in each MAC, since the UL resource schedulingnode is located in different node in the network side, i.e. one in MeNBand the other in SeNB.

The problem is how to use the information ‘data available fortransmission in PDCP’ in the MAC functions. If each MAC utilizes thesame information of ‘data available for transmission in PDCP’, both theMeNB and the SeNB would allocate UL resource that can cope with ‘dataavailable for transmission in PDCP’, in which case the ‘data availablefor transmission in PDCP’ is considered twice, and it leads to wastageof radio resource.

FIG. 9 is a conceptual diagram for allocating UL resources according toembodiments of the present invention.

To prevent the MeNB and SeNB to over-allocate the UL resource to the UEhaving dual RLC/MAC scheme, it is invented that the BS calculates andallocates UL resources by considering both a ratio of a buffer size tobe considered in each eNB and buffer size information reported by theUE.

The first eNB may transmit to a second eNB, uplink (UL) resourceallocation information for a user equipment (UE) connected with both thefirst eNB and the second eNB (S901).

Desirably, the first eNB may be the macro (or master) eNB in a macrocell and the second eNB may be the small (or secondary) eNB in a smallcell. A coverage of the macro cell is lager that a coverage of the smallcell. As mentioned earlier, the UE may be connected to both the macrocell and the small cell at the same time. And a plurality of small cells(e.g, micro cell, pico cell etc.) may be present in a big cell (e.g.macro cell) having larger coverage than the small cells for optimizationof data traffic, etc.

Desirably, the UL resource allocation information can be shared betweenthe first eNB and second eNB. An X2 signaling can be defined totransport the UL resource allocation information between them. The X2signaling means a signaling using an X2 interface between the first eNBand second eNB.

Desirably, the UL resource allocation information indicates a ratio ofthe buffer size to be considered in each eNB.

Specially, the UL resource allocation information may includetransmission rate (TR) information. The TR may define the ratio of“amount of PDCP data transmitted to a 1st RLC entity” to “amount of PDCPdata transmitted to a 2nd RLC entity” where the 1st RLC entity and the2nd RLC entity are connected to the PDCP entity on one direction.

The indication information can be a form of ratio “DATP-M:DATP-S”, orpercentile amount of DATP-S compared to DATP-M, or vice versa, or anytype of information that indicates the amount of data that can be usedto divide the DATP to DATP-M and DATP-S. Here, the ‘DATP-M’ means amountof data available for transmission in PDCP entity for a Macro cell MAC,and ‘DATP-S means amount of data available for transmission in PDCPentity for a Small cell MAC.

Desirably, the ratio of the buffer size may be configured per a radiobearer comprising one Packet Data Convergence Protocol (PDCP) entity,two Radio Link Control (RLC) entities and two Medium Access Control(MAC) entities for one direction.

The first eNB may receive from the UE, buffer size information (S903).In this case, there is no difference from the prior art in UE behaviorregarding calculation of DATP. Thus, the UE may report DATP as in theprior art, i.e. the UE does not divide DATP to DATP-M and DATP-S.

Desirably, the buffer size information may comprise amount of dataavailable for transmission in a PDCP entity (DATP) and amount of dataavailable for transmission in a RLC entity (DATR). In this case, thefirst eNB can receive from the UE, the DATP and DATR-M. Here, the‘DATR-M’ means amount of data available for transmission in RLC entityfor a Macro cell MAC.

The first eNB may determine and allocate one or more UL resources to theUE, by considering both of the buffer size information and the ULresource allocation information (S905-S907).

FIG. 10 is another conceptual diagram for allocating UL resourcesaccording to embodiments of the present invention.

The second eNB may receive from a first eNB, uplink (UL) resourceallocation information for a user equipment (UE) connected with both thefirst eNB and the second eNB (S901).

Desirably, the first eNB may be the macro (or master) eNB in a macrocell and the second eNB may be the small (or secondary) eNB in a smallcell. A coverage of the macro cell is lager that a coverage of the smallcell. As mentioned earlier, the UE may be connected to both the macrocell and the small cell at the same time. And a plurality of small cells(e.g, micro cell, pico cell etc.) may be present in a big cell (e.g.macro cell) having larger coverage than the small cells for optimizationof data traffic, etc.

Desirably, the UL resource allocation information can be shared betweenthe first eNB and second eNB. An X2 signaling can be defined totransport the UL resource allocation information between them. The X2signaling means a signaling using an X2 interface between the first eNBand second eNB.

Desirably, the UL resource allocation information indicates a ratio ofthe buffer size to be considered in each eNB.

Specially, the UL resource allocation information may includetransmission rate (TR) information. The TR may define the ratio of“amount of PDCP data transmitted to a 1st RLC entity” to “amount of PDCPdata transmitted to a 2nd RLC entity” where the 1st RLC entity and the2nd RLC entity are connected to the PDCP entity on one direction.

The indication information can be a form of ratio “DATP-M:DATP-S”, orpercentile amount of DATP-S compared to DATP-M, or vice versa, or anytype of information that indicates the amount of data that can be usedto divide the DATP to DATP-M and DATP-S. Here, the ‘DATP-M’ means amountof data available for transmission in PDCP entity for a Macro cell MAC,and ‘DATP-S means amount of data available for transmission in PDCPentity for a Small cell MAC.

Desirably, the ratio of the buffer size may be configured per a radiobearer comprising one Packet Data Convergence Protocol (PDCP) entity,two Radio Link Control (RLC) entities and two Medium Access Control(MAC) entities for one direction.

The second eNB may receive from the UE, buffer size information (S1003).In this case, there is no difference from the prior art in UE behaviorregarding calculation of DATP. Thus, the UE may report DATP as in theprior art, i.e. the UE does not divide DATP to DATP-M and DATP-S.

Desirably, the buffer size information may comprise amount of dataavailable for transmission in a PDCP entity (DATP) and amount of dataavailable for transmission in a RLC entity (DATR). In this case, thefirst eNB can receive from the UE, the DATP and DATR-S. Here, the‘DATR-S’ means amount of data available for transmission in RLC entityfor a Small cell MAC.

The second eNB may determine and allocate one or more UL resources tothe UE, by considering both of the buffer size information and the ULresource allocation information (S1005-S1007).

FIG. 11 is conceptual diagram an exemplary amount of data available fortransmission according to embodiments of the present invention.

An example procedure of this invention is shown in FIG. 11.

The MeNB and SeNB may exchange UL resource allocation information for aradio bearer (RB) via X2 interface signaling (S1101). In this example,the UL resource allocation information indicates the TR being set to 3:7(S1101).

For the indicated RB, the UE may report its buffer status includingDATP=1000 bytes, DATR-M=200 bytes, and DATR-S=300 bytes (S1103). In thisexample, the UE may report its buffer status indicated as 1200 byte tothe MeNB and 1300 byte to the SeNB.

In case of the MeNB, the MeNB may consider only TR fraction (e.g. 3/10)in UL resource allocation (S1107). Thus, the MeNB may allocate ULresource as 360 byte (because, 1200*( 3/10)=360) to the UE (S1109).

Similarly, in case of the SeNB, the SeNB may consider only TR fraction(e.g. 7/10) in UL resource allocation (S1111). Thus, the SeNB mayallocate UL resource as 910 byte (because, 1300*( 7/10)=910) to the UE(S1113).

This embodiment is not accurate because DATR is also divided by TR, butas long as DATR is small, the result would not create a practicalproblem. All the above mentioned methods can be applied to multipleRLC/MAC schemes, i.e. more than two RLC/MAC pairs. In this case, the TRmay be defined for all RLC/MAC pairs.

FIG. 12 is a block diagram of a communication apparatus according to anembodiment of the present invention.

The apparatus shown in FIG. 12 can be a user equipment (UE) and/or eNBadapted to perform the above mechanism, but it can be any apparatus forperforming the same operation.

As shown in FIG. 12, the apparatus may comprises a DSP/microprocessor(110) and RF module (transmiceiver; 135). The DSP/microprocessor (110)is electrically connected with the transciver (135) and controls it. Theapparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

Specifically, FIG. 12 may represent a UE comprising a receiver (135)configured to receive a request message from a network, and atransmitter (135) configured to transmit the transmission or receptiontiming information to the network. These receiver and the transmittercan constitute the transceiver (135). The UE further comprises aprocessor (110) connected to the transceiver (135: receiver andtransmitter).

Also, FIG. 12 may represent a network apparatus comprising a transmitter(135) configured to transmit a request message to a UE and a receiver(135) configured to receive the transmission or reception timinginformation from the UE. These transmitter and receiver may constitutethe transceiver (135). The network further comprises a processor (110)connected to the transmitter and the receiver. This processor (110) maybe configured to calculate latency based on the transmission orreception timing information.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term ‘eNB’ may be replaced with the term‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, forexample, by hardware, firmware, software, or a combination thereof.

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

While the above-described method has been described centering on anexample applied to the 3GPP LTE system, the present invention isapplicable to a variety of wireless communication systems in addition tothe 3GPP LTE system.

What is claimed is:
 1. A method for transmitting Buffer Status Reports(BSRs) by a user equipment (UE) in a wireless communication system, themethod comprising: receiving a configuration information from a basestation; generating a first BSR based on a first amount of dataavailable for transmission in a Packet Data Convergence Protocol (PDCP)entity and an amount of data available for transmission in a first RadioLink Control (RLC) entity belonging to a first cell; generating a secondBSR based on a second amount of data available for transmission in thePDCP entity and an amount of data available for transmission in a secondRLC entity belonging to a second cell; transmitting the first BSR to thefirst cell; and transmitting the second BSR to the second cell, whereinbased on the PDCP entity not dividing a total amount of user dataavailable for transmission in the PDCP entity according to theconfiguration by RRC, the first amount of data available fortransmission in the PDCP entity and the second amount of data availablefor transmission in the PDCP entity are indicated with same value as thetotal amount of user data available for transmission in the PDCP entity.2. The method according to claim 1, wherein a dual connectivity mode isconfigured for the UE.
 3. The method according to claim 1, when databecomes available for transmission in the first RLC entity, the firstRLC entity indicates the amount of data for transmission in the firstRLC entity to a first Medium Access Control (MAC) entity belonging tothe first cell, and when data becomes available for transmission in thesecond RLC entity, the second RLC entity indicates the amount of datafor transmission in the second RLC entity to a second MAC entitybelonging to the second cell.
 4. A user equipment (UE) operating in awireless communication system, the UE comprising: a radio frequency (RF)module; and a processor configured to control the RF module, wherein theprocessor is configured to: receive a configuration information from abase station; generate a first BSR based on a first amount of dataavailable for transmission in a Packet Data Convergence Protocol (PDCP)entity and an amount of data available for transmission in a first RadioLink Control (RLC) entity belonging to a first cell; generate a secondBSR based on a second amount of data available for transmission in thePDCP entity and an amount of data available for transmission in a secondRLC entity belonging to a second cell; transmit the first BSR to thefirst cell; and transmit the second BSR to the second cell, whereinbased on the PDCP entity not dividing a total amount of user dataavailable for transmission in the PDCP entity according to theconfiguration by RRC, the first amount of data available fortransmission in the PDCP entity and the second amount of data availablefor transmission in the PDCP entity are indicated with same value as thetotal amount of user data available for transmission in the PDCP entity.5. The UE according to claim 4, wherein a dual connectivity mode isconfigured for the UE.
 6. The UE according to claim 4, when data becomesavailable for transmission in the first RLC entity, the first RLC entityindicates the amount of data for transmission in the first RLC entity toa first Medium Access Control (MAC) entity belonging to the first cell,and when data becomes available for transmission in the second RLCentity, the second RLC entity indicates the amount of data fortransmission in the second RLC entity to a second MAC entity belongingto the second cell.